A numerical investigation of the plenum chamber aerodynamic behaviour of mechanical draught air-cooled heat exchangers

[摘要] ENGLISH ABSTRACT:The primary purpose of this dissertation is to further the understanding of the influence ofplenum chamber aerodynamic behaviour on mechanical draught air-cooled heat exchanger(ACHE) performance. The investigation, which included both forced and induced draughtACHEs, was conducted through the use of a commercially available computational fluiddynamics (CFD) code. A numerical axial flow fan and heat exchanger model that simulatesthe effect of the axial flow fan and heat exchanger bundle respectively on the flow fieldwithin the ACHE was developed and included in the CFD-code through user-programming.Where appropriate the numerical investigation was augmented with experimental data. Theplenum chamber aerodynamic behaviour is characterised and included in the draughtequations associated with forced and induced draught ACHEs through the introduction ofdimensionless plenum chamber recovery and plenum chamber loss coefficient respectively.The influence of changes made to a range of mechanical draught ACHEs on plenum chamberaerodynamic behaviour was investigated. These changes include:• Operating conditions of the axial flow fan.• The height of the plenum chamber in the fan axial direction.• The heat exchanger bundle isothermal flow resistance.• The fan to heat exchanger area ratio.• The axial position of the fan in the fan casing.From the results of the numerical investigation a set of design guidelines are set for bothforced and induced draught ACHEs. The design guidelines include recommended values forthe dimensionless plenum chamber recovery and plenum chamber loss coefficient to be usedin the respective draught equations enabling a more accurate prediction of the operating pointof a proposed mechanical draught ACHE.KEYWORDS: air-cooled heat exchangernumerical investigationplenum chamberaerodynamic behaviour

[发布机构] Stellenbosch University